Incremental feed mechanism



April 21, 1959 e. GROVE 2,332,649

' 'INCREMENTAL FEED MECHANISM Filed June 10. 1957 s Sheets-Sheet 1 rwit g IN VEN TOR.

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HTTOR NE Y6,

GEORGE L. GROVE.

April 21, 1959 v G. L JGR OVE v INCREMENTAL FEED MECHANISM Filed m 10. 1957 s Sheets-Sheet 2 ATTORNEYS.

United States Patent INCREMENTAL FEED MECHANISM George L. Grove, Cincinnati, Ohio, assignor to The Cincinnati Milling Machine 'Co., Cincinnati, Ohio, a corporation of Ohio Application June 10, 1957, Serial No. 664,683

7 Claims. (Cl. 51-103) This invention relates to a particular type of feed mechanism for machine tools and more particularly to one in which the feed is effected either in fine or coarse increments of predetermined magnitude. In grinding machines, for example, as the work is reduced in diameter due to wear of the wheel during grinding of the work piece, or as a result of truing of the wheel between successive grinding operations, it becomes necessary to compensate for the reduction in size of the wheel in order to prevent oversize parts from being produced. This compensation occurs in one direction only and may be conveniently introduced by an incremental feed mechanism which is capable of moving the axis of the wheel closer to the axis of the work either in fine increments to compensate for wear of the wheel, or in coarse increments to compensate for the amount of material removed from the wheel during truing. This type of compensation is particularly adapted for use with centerless grinders where post gauging of the work is utilized for controlling the size of the work, i.e., where the work is gauged after it leaves the machine.

Accordingly, it is an object of the present invention 2 applied to a centerless grinder of the infeed type with manually operable push buttons for effecting the com pensation. It will be appreciated, as the description proceeds, however, that the invention might equally well be applied to a center type grinder or to a through-feed centerless grinder.

As shown in Fig. 1, the grinder is provided with a base 10 on which is supported a grinding wheel 11 for rotation about an axis which is fixed with respect to the base 10. The work piece 12 to be ground is supported on a work rest blade 13 and is pressed against the wheel 11 by a second grinding wheel 14 which rotates at reduced speed and serves to regulate or control the rotation of the work piece 12 as it is being ground by the wheel 11. The wheel 14 is carried by a cross slide 15 which is guided by ways 16 carried by a lower slide 17. The lower slide is suitably guided for sliding movement on the base 10 and carries at its forward end the work rest blade 13 as illustrated in Fig. 1. A clamp 18 is provided for securing the cross slide 15 to the lower slide 17 so that the two will move as a unit on the base 10. A second clamp 19 is provided for securing the lower slide to the base whereupon the cross slide may be traversed along the lower slide by releasing the clamp 18.

For set-up purposes the cross slide is provided witha hand wheel 20 which is adapted to rotate a nut journaled in the cross slide and meshing with a feed screw. This mechanism is fully explained and described in US. Patent No. 2,709,877, patented June 7, 1955, in the names of Albert H. Dali and George L. Grove. In setting up the machine, the cross slide 15 is clamped to the lower slide 17 by tightening clamp 18, and clamp 19 is loosened to to provide an incremental feed mechanism which is preset to enter the desired amount of compensation quickly and accurately either before, after, or during a machining operation.

Another object of the invention is to provide a compensating mechanism which is adapted for use with grinding machines of either the infeed type or the throughfeed type.

Another object of the invention is to provide a novel type of feed mechanism which is adapted to provide compensation either in fine increments or in coarse increments as may be required.

With these and other objects in view which will become apparent from the following description, the invention includes certain novel features of construction and combinations of parts, the essential elements of which are set forth in the appended claims, and a preferred form or embodiment of which will hereinafter be described with reference to the drawings accompanying this application.

In the drawings Fig. 1 is a front view of a machine embodying the principles of the present invention.

Fig. 2 is a front elevation of a portion of the machine shown in Fig. 1 with parts broken away to show the permit the lower slide to move with respect to the base 10. The hand wheel 20 is then turned to feed the cross slide 15 and lower slide 17 as a unit along the feed screw until the work rest blade 13 is brought into the proper position. The clamp 19 is then tightened and the clamp 18 loosened to permit the desired setting of the wheel 14 independently of the work rest blade 13. The clamp 21 (Fig. 1) is then tightened to clamp the nut with respect to the cross slide 15 as explained in the aforementioned patent to thereby enable feeding movement of the cross slide to be effected by rotation of the feed screw.

As shown in Fig. 2, the machine is desirably provided with the walking beam structure disclosed in US. Patent No. 2,718,101, patented September 20, 1955, in the names of Albert D. C. Stuckey and Jacob Decker. As herein in the present machine the sleeve is journaled for rotation on the feed screw by means of a thrust bearing 35 anda combined radial and thrust bearing 36. These bearings are interposed between the feed screw 23 and the sleeve 34 and are held in place between a nut 38 threaded on I the feed screw and a shoulder 37 likewise provided on connection between the present invention and the prior the feed screw. As explained in the A. D. C. Stuckey et a1. patent, the Walking beam operates to bodily move the feed screw in an axial direction to effect rapid traverse movement of the cross slide for infeed movement of the grinding wheel 14 with respect to the grinding wheel 11.

Inasmuch as in the present construction the feed screw 23 is journaled for rotation with respect to the walking beam 29, it is desirable for set-up purposes to provide a clamp screw 39 (Fig. 2) received in a tapped hole provided in the pivot pin 30 with the inner end of the screw adapted to bear against the feed screw and thereby secure the latter against rotation when the clamp screw 39 is tightened. This will prevent rotation of the feed screw when the handwheel 20 is turned to rotate the nut during I the setup of the machine. In the following description of the incremental feed mechanism for the cross slide 15 it will be assumed that the machine has been properly set up and that the clamp screw 39 has been loosened so as to permit rotation of the feed screw. It will also be assumed that the clamp 21 (Fig. 1) has been tightened so as to prevent rotation of the nut in the cross slide whereby rotation of the feed screw will effect feeding movement of the cross slide.

Secured to the right hand end of the base is a frame 45 which provides support for the incremental feed mechanism for the grinding wheel 14. The frame 45 is adapted to be secured to the base by suitable fastening means including the studs 46. The frame is provided with a cover or housing 47 for enclosing the mechanism supported by the frame. As shown in Figure 2, the feed screw 23 is provided near its right hand end with screw threads for receiving a stop nut 48. The nut 48 is arranged to be held against rotation on the feed screw 23 by means of a set screw, as shown, and is provided with a face 49 which is adapted to engage against a finished end face 50 provided on the right hand end of the base.

On the right hand end of the feed screw 23 there is fixedly secured a gear 51 which is held on the shaft by a retaining nut 52. The gear 51 meshes with a pinion 53 fast on a shaft 54 which is journaled for rotation in anti-friction bearings 55 and 56 mounted in the frame 45.

Supported on the shaft 54 by anti-friction bearings 57 and 58 is a gear member 60 which comprises an elongated hub 61 on either end of which is formed spur gears 62 and 63. The interior of the hub 61 is provided with a longitudinally extending keyway 64 which is adapted to receive a key 65 which enters a corresponding keyway provided inthe casing of a cam clutch 66 of conventional design. This clutch is of the type containing a series of circumferentially arranged sprags or cams which bear against the surface of the shaft 54 so as to drive the shaft in one direction of rotation of the gear member 60 while permitting free rotation of the latter member with respect to the shaft in the other direction of rotation.

As best shown in Figs. 3 and 5, the gear teeth 63 are adapted to mesh with rack teeth 67 provided on a plunger 68, while the gear teeth 62 are adapted to mesh with rack teeth 69 formed on a plunger 70. The plunger 68 is adapted to control coarse incremental feeding movement of the cross slide while the plunger 70 is adapted to control fine incremental feeding movement thereof.

Considering first the control effected by the plunger 68 (Fig. 3), it will be observed that this plunger is received for axial sliding movement within a bore 75 provided in the frame 45. The plunger is shown in Fig. 3 in its normal or home position and is adapted to be moved toward the left in a manner hereinafter to be described when a coarse increment of feeding movement is to be given to the cross slide 15. Left hand movement of the plunger is limited by a micrometer screw 76 which is provided with threads 77 adapted to mesh with corresponding threads formed in a bushing 78 bolted to the frame 45. At its left hand end the screw 76 is fitted with a knurled dial 79 which is secured to the screw 76 by set screws as shown. The bushing 78 is provided with an outwardly extending hub 80 which may be internally threaded to receive a stop nut 81 which cooperates with a shoulder 82 formed on a screw 76 to limit outward movement of the screw when the dial is rotated counterclockwise.

As shown in Fig. 4, the hub 80 may be provided with graduations 83 signifying the amount of incremental movement provided to the cross slide on each reciprocation of the plunger 68. Each graduation 83 may, for example, represent .00025" of movement of the cross slide per reciprocation of the plunger, and-each complete revolution of the dial 79 may, for example, represent .0005" of travel of the cross slide. The dial 79 may be provided with an index 84 which cooperates with an index'SS providcdonthe hub. 80 for providing a precise indication of the setting of the screw 76. The limits of travel permitted the plunger 68 by the screw 76 may, for example, be such as to enable the incremental movement of the cross slide to be varied from .0005" to .002" per reciprocation of the plunger. In Fig. 3 the dimension Y represents the spacing between the left hand end of the plunger 68 and the right hand end of the micrometer screw 76, this being the amount of left hand movement permitted the plunger 68 when it is reciprocated by the means hereinafter to be described. This distance may be increased or diminished by rotation of the dial 79 in one direction or the other to thereby increase or decrease the amount of coarse feeding movement which will be given to the cross slide 15 upon reciprocation of the plunger.

Referring now to Fig. 5, it will be seen that the fine" plunger 70 is, like the coarse plunger 68, mounted for axial sliding movement within a bore 90, provided in the frame 45. Right hand movement of the plunger 70 is limited by a stop 91 which is secured to the frame 45 and is provided with an abutment face 92 which cooperates with a corresponding abutment face provided on the right hand end of plunger 70. Left hand movement of the plunger is limited by a piston 93 which is fitted for sliding movement within the bore and which is provided with an abutment face 94 adapted to cooperate with a corresponding abutment face provided on the left hand end of the plunger 70. As will hereinafter be described, fluid pressure is admitted into the bore 90 between the plunger 70 and the piston 93, thereby tending to separate these elements and maintain them in the positions shown in Fig. 5. Left hand movement of the piston 93 under the influence of the pressure fluid acting upon its right hand end is determined by a micrometer screw 95 which is threaded at 96 and provided at its left hand end with a knurled dial 97. This dial is fastened securely to the end of the screw 95 by means of suitable set screws and is bored to receive a hub 98 formed on the end of a bushing 99. The bushing 99 forms the end closure of a hydraulic cylinder 100 fastened to the frame 45 in axial alignment with the bore 90. Fitted within the cylinder 100 is a sleeve 101 and a piston 102 having a head portion fitted with sealing rings 103. The left hand end of the piston is of reduced diameter and is fitted for sliding movement within the sleeve 101. The piston 102 is also provided with an axially extending bore for receiving the screw 95, the threads 96 of which have threaded engagement with corresponding internal threads provided in the left hand end of the piston 102. Rotation of the piston 102 is prevented by a pin 104 mounted in the bushing 99 and extending into a hole provided therefor in the left hand end of the piston. The screw 95 is formed at its right hand end with a threaded portion 105 for receiving a stop nut 106 which limits outward movement of the screw 95 upon counterclockwise rotation of dial 97.

As will hereinafter be described, the cylinder 100 is ported so as to permit hydraulic fluid under pressure to enter the chamber 107 between the head of piston 102 and the sleeve 101, thereby holding the piston in its right hand position, as shown in Fig- 5, with the right hand end of the piston abutting against the end wall 108 of the frame 45. The screw 95 is thereby held in the position shown in Fig. 5 with its right hand end limiting left hand movement of the piston 93 to serve as 'a stop for the plunger 70 and to limit left hand movement thereof to the extent indicated by the dimensionX which represents the spacing between the abutment faces 94. By rotating the dial 97 in one direction or theother, the dimension X may be increased or decreased, thereby varying the incremental feeding movement of the cross slide 15 under the control of the plunger 70. The hub 98, like the hub 80, may be provided with graduations indicating the incremental movement which will be provided to the cross slide upon each reciprocationof the plunger 70. For example, the hub-may have inscribed thereon graduations representing .0001" of movement of the cross slide, and each revolution of the dial 97 may conveniently correspond to .0002" of movement of the cross slide. The dial 97 may also bear circumferential graduations, each of which may, for example, represent .000050" of movement of the cross slide per reciprocation of the plunger. The range of movement of the cross slide controlled by the plunger 70 may conveniently extend from .000050" to .0005", thereby enabling the machine operator to select a suitable increment of feed within this range by proper setting of the dial 97.

The means for controlling the plunger 70 and the piston 102 is shown in Fig. 6 of the drawings. This means includes a pair of solenoid operated valves 115 and 116 which are connected in the hydraulic circuit as shown in Fig. 6. Fluid under pressure for operating the plunger and piston is provided by a pump 117 which draws fluid from a sump 118 and delivers it under pressure to a line 119. The pressure in the line 119 may be maintained constant by a relief valve 120 connected to the pressure line and discharging into the sump 118.

The valve 115 which controls the plunger 70 is fitted with aspool 121 which is urged toward the left by a spring ;122. At its left hand end the valve is fitted with a solenoid 123 which, when energized, will move the spool 121 to the right against the bias of the spring 122. Energizing current for the solenoid may be obtained from a pair of power lines 124 connected to any suitable source of supply current. To energize the solenoid, a manually operable push button 125 may be depressed, therebyconnecting the solenoid to the power lines 124.

When the solenoid is deenergized with the spool 121 in its left hand position as shown in Fig. 6, fluid under pressure will be delivered from line 119 through a line 128 to the space existing between the left hand end of plunger 70 and the right hand end of piston 93. As previously mentioned, this will tend to separate the elements and maintain the plunger 70 in its right hand position as determined by engagement of the abutment faces 92. At the same time, a line 129 which is communicatively connected with the space between the right hand end of plunger 70, and the stop 91 will be connected to an exhaust line 130 which returns fluid to the sump 118. However, when the solenoid 123 is energized, the spool 121 will be moved toward the right, thereby connecting the fluid pressure line 119 with the line 129 so as to apply pressure to the right hand end of the plunger 70. Simultaneously, the line 128 will be connected with a line 131 which is connected to the exhaust line 130, thereby removing pressure from the left hand end of the plunger 70. Accordingly, the plunger 70 will be moved to the left to the extent permitted by the piston 93 which is represented by the distance X in Fig. 5. The rack teeth 69 on the plunger 70 will thereby rotate the gear 62 in a clockwise or driving direction and cause the feed screw 23 to be rotated counterclockwise as viewed in Fig. 5 to provide fine incremental feeding movement of the cross slide 15. When the solenoid 123 is deenergized, upon releasing of the push button 125, the spring 122 will return the spool 121 to the position shown in Fig. 6, thereby shifting the plunger 70 to the right to its normal position as shown in Fig. 6. The clutch 66 (Fig. 2) limits the feeding movement to one direction only. Hence, each time the push button 125 is depressed and released, an increment of feeding movement will be provided to the cross slide under the control of the fine plunger 70.

The valve 116 which controls movement of the piston 102 is fitted with a spool 135 which is biased toward the left by a spring 136. This valve is fitted with a solenoid 137 which, when energized, will move the spool toward the right against the bias of the spring 136. When the spool is in its left hand end position, as shown in Fig. 6, the fluid pressure line 119 will be connected with a line 138 which is communicatively connected with the chamber 107 existing between the head of piston 102 and the sleeve 101. As previously stated, this will urge the piston 102 toward the right and maintain the end of the piston against the end wall108 of the frame 45. Since the area of the piston 102 acted upon by the pressure from line 119 is greater than the area of the piston 93, the force exerted on the latter piston will be less than the force on piston 102 so that the latter will act as a rigid stop so long as pressure is applied to the line 138.

The solenoid 137 is adapted to be energized by depression of a push button 140 which serves to connect the solenoid to the power lines 124. As shown, the pushbutton 140 will also connect the solenoid 123 to the power line, thereby energizing this solenoid simultaneously with the solenoid 137. When the latter solenoid is energized, the spool 135 will be moved toward the right against the bias ofspring 136, thereby connect ing the line 138 with a line 141 which is connected to the exhaust line 130. Thereby, the space 107 between the head of piston 102 and sleeve 101 will be connected to exhaust and so permit the piston 102 to move toward the left. Energization of solenoid 123 will, as previously described, connect pressure to the line 129 to drive the plunger 70 to the left. The gear member 60 will accordingly be rotated clockwise to the extent permitted by the coarse plunger 68 (Fig. 3) since the microm eter screw (Fig. 5) no longer serves as a stop for the plunger 70. Hence, a coarse increment of feeding movement will be provided to the cross slide 15 in accordance with the setting of the micrometer screw 76 which controls the movement of the plunger 68.

When the push button 140 is released, the solenoids 123 and 137 will be deenergized, thereby restoring the spools of valves and 116 to the position shown in Fig. 6. Accordingly, pressure will again be supplied to the lines 138 and 128 to return the plunger 70 to its normal position as shown in Fig. 6. It will be understood, therefore, that the drive for the feeding mechanism is supplied by the plunger 70, the plunger 68 being driven thereby through the gear member 60 and serving as a limit stop to determine the amount of incremental feeding movement provided to the cross slide.

While in the foregoing specification I have set forth a specific structure in considerable detail for the purpose of illustrating a particular embodiment of my invention, it will be understood that such details of structure may be varied by those skilled in the art without departing from the spirit of the invention as defined by the claims.

I claim:

1. In a grinding machine having a base, a cross slide supported on said base, and a grinding wheel carried by said cross slide, the combination of a feed screw having a threaded connection with said cross slide for effecting feeding movement of said wheel, means journaled on said feed screw for translating said screw axially with respect to said base to provide rapid traverse movement of said wheel, and means for advancing said cross slide in increments of predetermined extent relative to said translating means, said means comprising a plunger arranged to have a limited stroke of reciprocatory movement, a one-directional drive transmission between said plunger and said feed screw for giving the latter an increment of rotation in one direction on each reciprocation of said plunger, and selectively operable means for effecting a single reciprocation of said plunger whereby said wheel will be moved in an incremental distance relative to said translating means.

2. In a grinding machine having a base, a cross slide supported on said base and a grinding wheel carried by said cross slide, the combination of a feed screw having a threaded connection with said cross slide for effecting feeding movement of said wheel relative to said base, a first plunger arranged for limited reciprocatory movementof one degree of magnitude, a second plunger arranged for limited reciprocatory movement of a second degree of magnitude, a one-directional drive transmission between said plungers and said feed screw for giving the latter increments of rotation in one direction in accordance with movement of one or the other of said plungers, and selectively operable means for eflfecting a single reciprocating of said plungers and for determining which of said plungers shall be effective to control the extent of feeding movement of the wheel relative to said base.

3. In a machine tool having a base and a cross slide supported on said base, the combination of a feed screw having a threaded connection with said cross slide for effecting movement thereof, a reciprocatory plunger, normally eflective means for limiting the reciprocatory movement of said plunger, a one-directional drive transmission between said plunger and said feed screw for giving the latter an increment of rotation in one direction on each reciprocation of said plunger, selectively operable means for effecting a single reciprocation of said plunger and a corresponding incremental rotation of said feed screw, and a second selectively operable means for disabling said limiting means to permit additional movement of said plunger.

4. The machine tool of claim 3 including a second means for limiting the stroke of said plunger when said first-mentioned limiting means is disabled.

5. The machine tool of claim 3 wherein said limiting means includes a fluid pressure operated piston, a fixed stop for limiting movement of said piston under the influence of the fluid pressure acting thereon, and wherein said disabling means includes means for releasing the fluid pressure acting on said piston to permit it to move away from said stop and thereby allow additional move-' ment of said plunger.

6. The machine tool of claim 5. including means for positively limiting the additional movement of said plunger to a predeterminedamount.

7. In a grinding machine having a base, a cross slide supported on said base and a grinding wheel carried by said cross slide, the combination of a feed screw having a threaded connection with said cross slide for effecting feeding movement of said wheel relative to said base, a reciprocatory plunger, fluid pressure means for operating said plunger, normally effective means for limiting the reciprocatory movement of said plunger to a given degree of magnitude, a second reciprocatory plunger, means for limiting the reciprocatory movement of said second plunger to a degree of magnitude greater than that of said first-mentioned plunger, rack teeth carried by each of said plungers, a unitary gear member meshing with the rack teeth on both of said plungers, a one-directional drive transmission between said gear member and said feed screw for giving the latter increments of rotation in one direction selectively operable means for causing said fluid pressure means to give said first-mentioned plunger a single cycle of operation, and a second selectively operable means for disabling said normally effective limiting means to permit said second plunger to control the extent of incremental movement given to said feed screw by said gear member.

References Cited in the file ofthis patent UNITED STATES PATENTS 2,709,877 Dall et al. June 7, 1955 

